Day and night (symbol)
Throughout the poem, day and night symbolize life and death, respectively. Just as a day eventually ends, so does life. Life is characterized as possessing the brightness, happiness, and vibrancy of day, while death is dark, lonely, and gloomy like night. Yet in spite of this negative image, death is as inevitable after life as night is after day. Thomas thus suggests that life and death are part of a natural cycle beyond our control and even comprehension. The cycle of day and night is endless, extending beyond the amount of time we can fathom, as does death—and also, perhaps, one's legacy, which is why we should "rage" against death and attempt to overcome it. While this effort will inevitably fail, it will produce a legacy that outlives us.
Lightning and meteors (symbol)
Continuing the association of brightness with life, Thomas uses lightning and meteors to represent the vitality of life. Just as they light up the sky, they add vivacity to life and have the ability to lend a legacy to the dying. The men who "redirect lightning" change the world meaningfully, while those whose eyes “blaze like meteors” fight courageously and defiantly in the face of death. By comparing these men's eyes to something celestial and inorganic, incomprehensibly hot and fast, Thomas indicates that there's something sublime and impossible to understand about human life, and death as well.
